| Message ID | 20231203085806.120240-2-andrea.righi@canonical.com |
|---|---|
| State | New |
| Headers | show |
| Series | [N/U,1/1] UBUNTU: SAUCE: rcu: Provide a boot time parameter to control lazy RCU | expand |
On Sun, 3 Dec 2023 at 08:59, Andrea Righi <andrea.righi@canonical.com> wrote: > > From: Qais Yousef <qyousef@layalina.io> > > BugLink: https://bugs.launchpad.net/bugs/2045492 > > To allow more flexible arrangements while still provide a single kernel > for distros, provide a boot time parameter to enable/disable lazy RCU. > > Specify: > > rcutree.enable_rcu_lazy=[y|1|n|0] > > Which also requires > > rcu_nocbs=all > > at boot time to enable/disable lazy RCU. > > To disable it by default at build time when CONFIG_RCU_LAZY=y, the new > CONFIG_RCU_LAZY_DEFAULT_OFF can be used. > > Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io> > (cherry picked from https://lore.kernel.org/lkml/20231203011252.233748-1-qyousef@layalina.io/T/#u) > Signed-off-by: Andrea Righi <andrea.righi@canonical.com> > --- > Documentation/admin-guide/kernel-parameters.txt | 5 +++++ > kernel/rcu/Kconfig | 13 +++++++++++++ > kernel/rcu/tree.c | 7 ++++++- > 3 files changed, 24 insertions(+), 1 deletion(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index b9c7a580f7ec..189020bf0ae9 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -5031,6 +5031,11 @@ > this kernel boot parameter, forcibly setting it > to zero. > > + rcutree.enable_rcu_lazy= [KNL] > + To save power, batch RCU callbacks and flush after > + delay, memory pressure or callback list growing too > + big. > + > rcuscale.gp_async= [KNL] > Measure performance of asynchronous > grace-period primitives such as call_rcu(). > diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig > index bdd7eadb33d8..e7d2dd267593 100644 > --- a/kernel/rcu/Kconfig > +++ b/kernel/rcu/Kconfig > @@ -314,6 +314,19 @@ config RCU_LAZY > To save power, batch RCU callbacks and flush after delay, memory > pressure, or callback list growing too big. > > + Requires rcu_nocbs=all to be set. > + > + Use rcutree.enable_rcu_lazy=0 to turn it off at boot time. > + > +config RCU_LAZY_DEFAULT_OFF > + bool "Turn RCU lazy invocation off by default" > + depends on RCU_LAZY > + default n > + help > + Allows building the kernel with CONFIG_RCU_LAZY=y yet keep it default > + off. Boot time param rcutree.enable_rcu_lazy=1 can be used to switch > + it back on. > + > config RCU_DOUBLE_CHECK_CB_TIME > bool "RCU callback-batch backup time check" > depends on RCU_EXPERT > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 3ac3c846105f..8b7675624815 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -2719,6 +2719,9 @@ __call_rcu_common(struct rcu_head *head, rcu_callback_t func, bool lazy_in) > } > > #ifdef CONFIG_RCU_LAZY > +static bool enable_rcu_lazy __read_mostly = !IS_ENABLED(CONFIG_RCU_LAZY_DEFAULT_OFF); > +module_param(enable_rcu_lazy, bool, 0444); > + > /** > * call_rcu_hurry() - Queue RCU callback for invocation after grace period, and > * flush all lazy callbacks (including the new one) to the main ->cblist while > @@ -2744,6 +2747,8 @@ void call_rcu_hurry(struct rcu_head *head, rcu_callback_t func) > __call_rcu_common(head, func, false); > } > EXPORT_SYMBOL_GPL(call_rcu_hurry); > +#else > +#define enable_rcu_lazy false > #endif > > /** > @@ -2792,7 +2797,7 @@ EXPORT_SYMBOL_GPL(call_rcu_hurry); > */ > void call_rcu(struct rcu_head *head, rcu_callback_t func) > { > - __call_rcu_common(head, func, IS_ENABLED(CONFIG_RCU_LAZY)); > + __call_rcu_common(head, func, enable_rcu_lazy); > } > EXPORT_SYMBOL_GPL(call_rcu); > > -- > 2.40.1 > > > -- > kernel-team mailing list > kernel-team@lists.ubuntu.com > https://lists.ubuntu.com/mailman/listinfo/kernel-team
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index b9c7a580f7ec..189020bf0ae9 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5031,6 +5031,11 @@ this kernel boot parameter, forcibly setting it to zero. + rcutree.enable_rcu_lazy= [KNL] + To save power, batch RCU callbacks and flush after + delay, memory pressure or callback list growing too + big. + rcuscale.gp_async= [KNL] Measure performance of asynchronous grace-period primitives such as call_rcu(). diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig index bdd7eadb33d8..e7d2dd267593 100644 --- a/kernel/rcu/Kconfig +++ b/kernel/rcu/Kconfig @@ -314,6 +314,19 @@ config RCU_LAZY To save power, batch RCU callbacks and flush after delay, memory pressure, or callback list growing too big. + Requires rcu_nocbs=all to be set. + + Use rcutree.enable_rcu_lazy=0 to turn it off at boot time. + +config RCU_LAZY_DEFAULT_OFF + bool "Turn RCU lazy invocation off by default" + depends on RCU_LAZY + default n + help + Allows building the kernel with CONFIG_RCU_LAZY=y yet keep it default + off. Boot time param rcutree.enable_rcu_lazy=1 can be used to switch + it back on. + config RCU_DOUBLE_CHECK_CB_TIME bool "RCU callback-batch backup time check" depends on RCU_EXPERT diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 3ac3c846105f..8b7675624815 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2719,6 +2719,9 @@ __call_rcu_common(struct rcu_head *head, rcu_callback_t func, bool lazy_in) } #ifdef CONFIG_RCU_LAZY +static bool enable_rcu_lazy __read_mostly = !IS_ENABLED(CONFIG_RCU_LAZY_DEFAULT_OFF); +module_param(enable_rcu_lazy, bool, 0444); + /** * call_rcu_hurry() - Queue RCU callback for invocation after grace period, and * flush all lazy callbacks (including the new one) to the main ->cblist while @@ -2744,6 +2747,8 @@ void call_rcu_hurry(struct rcu_head *head, rcu_callback_t func) __call_rcu_common(head, func, false); } EXPORT_SYMBOL_GPL(call_rcu_hurry); +#else +#define enable_rcu_lazy false #endif /** @@ -2792,7 +2797,7 @@ EXPORT_SYMBOL_GPL(call_rcu_hurry); */ void call_rcu(struct rcu_head *head, rcu_callback_t func) { - __call_rcu_common(head, func, IS_ENABLED(CONFIG_RCU_LAZY)); + __call_rcu_common(head, func, enable_rcu_lazy); } EXPORT_SYMBOL_GPL(call_rcu);